This invention relates to dynamoelectric machines and in particular to AC induction motors. While the invention is described with particular emphasis on the use of the motor of this invention in ceiling fan applications, those skilled in the art will recognize the wider applicability of the inventive concepts disclosed hereinafter.
Ceiling fans, alone or in combination with other electrical devices, for example, lights, light fixtures, or luminaires have recently again become exceedingly popular. Most ceiling fan technology dates from the turn of the century, when such fans were used extensively. The prior demise of the ceiling fan was coincident with the rise of the use of refrigerated air conditioning systems in the 1940's and 50's. The relatively recent acceleration in energy costs, however, has caused the consumer to look for alternate ways to "condition" air. In particular, it has been found that a ceiling fan can be used during the heating season to return hot air from the ceilings of relative high ceiling rooms toward the floor, providing an air pattern which maintains a more constant temperature gradient in such rooms at a lower thermostat setting, with lower overall operating cost. Likewise, such air circulation during the cooling season permits a higher thermostat setting. Again, the improved temperature gradient from floor to ceiling reduces overall energy consumption resulting in lower operating costs. Consequently, the ceiling fan has regained its popularity for a range of applications, from factories to resort condominiums.
Historically, ceiling fan motors have been of two general types. The first, known in the art as an inside/out motor, positioned the rotor externally of the stator and permitted direct attachment of the fan blades to the rotor. Since the stator assembly was positioned internally of the rotor, a stationary shaft was inserted through the stator core. The stationary shaft made the attachment of additional electrical components easy to accomplish. Unfortunately, inside/out motors are relatively expensive to produce. They also weigh relatively large amounts in comparison to more conventional motor designs. Consequently, their installation is complicated and cannot easily be accomplished by a single individual.
More conventional stator/rotor motor designs also have been employed in ceiling fan applications. Conventional motors do not lend themselves to ceiling fan applications as readily as inside/out motors in that they do not provide an easy way to attach additional devices to the ceiling fan. In particular, the addition of a light or a lighting fixture to the ceiling fan structure is difficult to accomplish with conventional stator/rotor designs because the rotor for the motor is located in the central bore of the stator assembly, and rotates during motor operation. I am aware of motor designs of the conventional stator/rotor type in which a large sleeve bearing has been used in conjunction with a second stationary shaft. The stationary shaft facilitates attachment of the above-mentioned luminaires or other electrical devices. However, the design and construction of such prior art motors have produced products having severe weight handicaps. For example, one prior art design with which I am familiar requires additional support for the ceiling fan if the fan is to be installed in a home. That is to say, the fan cannot be hung from a conventional ceiling electrical box. Rather, additional braces are required along the ceiling rafters for safety purposes. Because of its weight, installation of such prior art ceiling fans by a single individual is nearly impossible.
The invention disclosed hereinafter overcomes these prior art deficiencies by providing a single motor structure which can be used over a broad range of ceiling fan designs and applications. In its industrial form, it may be used without a decorative enclosure and provides a very light, easy to install product. In cases where asthetic appearance is important, the design enables the insertion of the motor in a decorative enclosure, so that the motor per se is hidden. Even with such an enclosure, however, the fan is light weight and can be installed in a conventional manner without use of additional supports or braces. Installation by a single individual is not only possible but practical. The motor includes a stationary center shaft which is used both for the attachment of additional components, and to provide a cableway for connection of those devices to a source of electrical energy.
One of the objects of this invention is to provide an improved motor design for ceiling fan applications.
Another object of this invention is to provide a relatively light weight motor design.
Another object of this invention is to provide a motor design adapted for ceiling fan applications which includes a stationary center shaft.
Another object of this invention is to provide a motor for ceiling applications which can be used on a broad range of those applications, including industrial and residential uses.
Another object of this invention is to provide a simplified motor construction method of assembly.
Still another object of this invention is to provide a simplified motor design which can be placed in an asthetically appealing enclosure simply and economically.
Other objects of this invention will be apparent to those skilled in the art in light of the following description and accompanying drawings.